For the purpose of setting optimum operating conditions, turbomachines such as aircraft engines routinely have at least one compressor-side, adjustable stationary blade row (that does not rotate around the engine machine axis) including a plurality of stationary blades which are pivotable around their main axis or blade axis. Together with an inner ring which encompasses a rotor section, the stationary blade row forms a stationary blade ring. The inner ring is used for the inner stabilization and support of the stationary blades and usually has a plurality of radial bearing holes, into which the bearing bushes are inserted for accommodating a blade-side bearing journal.
As shown, for example, in DE 10 2007 015 669 A1, and related WO 2008/119325, hereby incorporated by reference herein, an inner ring may be divided into two half rings on a horizontal housing parting plane of the turbomachine, these half rings, in turn, being divided along an axial parting plane into a front half ring segment and a rear half ring segment. The half ring segments are assembled in the axial direction around the bearing journals of the stationary blades and mounted with the aid of axial connecting elements, such as pins or screws, which are inserted between the adjacent bearing journals. A seal carrier having run-in coatings on its inner circumferential side is pushed onto the half ring segments in the circumferential direction for sealing a radial clearance between the inner ring and a diametrically opposed rotor section. However, the positioning of the axial connecting elements requires a minimum clearance between the bearing bushes, which has a limiting effect on a minimum engine size.
Composing the inner ring from two half rings which are undivided in the axial direction is alternatively proposed in DE 10 2006 024 085 A1 and related U.S. Pat. No. 8,376,692, hereby incorporated by reference herein. The half rings are elastically deformable in such a way that they may roll over the bearing journals of the stationary blades mounted in housing halves. The half rings are pretensioned to a constant tensioning radius, positioned in the area of the bearing journals and then relaxed. However, a separate seal carrier for sealing a radial clearance between the inner ring and a diametrically opposed rotor section is also required in this variant.
Providing the ring segments of an inner ring, which is undivided in the axial direction, with a circumferential angle which is much smaller than 180°, is proposed in U.S. Pat. No. 4,395,195 A. This permits assembly without elastic deformation of the ring segments. The ring segments are each pushed onto a bearing body in the circumferential direction and coupled on their abutment surfaces in a form-locked manner. The bearing bodies are used to support at least two stationary blades and have the same circumferential angle as the ring segments. However, vibration problems arise due to the large number of ring segments. Furthermore, potential leakage paths are formed in the area of the ring segment abutment surfaces. To seal a radial clearance between the inner ring and a diametrically opposed rotor section, the ring segments are provided with run-in coatings on the inner circumferential side.